Temporal and Spatial Variation of Toxic Metal Concentrations in Cultivated Soil in Jiaxing, Zhejiang Province, China: Characteristics and Mechanisms.

The toxic metal (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) pollution in 250 agricultural soil samples representing the urban area of Jiaxing was studied to investigate the temporal and spatial variations. Compared to the early 1990s, the pollution level has increased. Industry and urbanization were the main factors causing toxic metal pollution on temporal variation, especially the use of feed containing toxic metals. The soil types and crop cultivation methods are the main factors causing toxic metal pollution on spatial variation. Although the single-factor pollution indices of all the toxic metals were within the safe limits, as per the National Soil Environmental Quality Standard (risk screening value), if the background values of soil elements in Jiaxing City are used as the standard, the pollution index of all the elements surveyed exceeds 1.0, reaching a level of mild pollution. The soil samples investigated were heavily contaminated with toxic metal compounds, and their levels increased over time. This situation poses potential ecological and health risks.

Body size: A hidden trait of the organisms that influences the distribution of antibiotic resistance genes in soil.

Body size is a key life-history trait of organisms, which has important ecological functions. However, the relationship between soil antibiotic resistance gene (ARG) distribution and organisms' body size has not been systematically reported so far. Herein, the impact of organic fertilizer on the soil ARGs and organisms (bacteria, fungi, and nematode) at the aggregate level was analyzed. The results showed that the smaller the soil aggregate size, the greater the abundance of ARGs, and the larger the body size of bacteria and nematodes. Further analysis revealed significant positive correlations of ARG abundance with the body sizes of bacteria, fungi, and nematodes, respectively. Additionally, the structural equation model demonstrated that changes in soil fertility mainly regulate the ARG abundance by affecting bacterial body size. The random forest model revealed that total phosphorus was the primary soil fertility factor influencing the body size of organisms. Therefore, these findings proposed that excessive application of phosphate fertilizers could increase the risk of soil ARG transmission by increasing the body size of soil organisms. This study highlights the significance of organisms' body size in determining the distribution of soil ARGs and proposes a new disadvantage of excessive fertilization from the perspective of ARGs.

Collective self-optimization of binary mixed heterogeneous populations.

To maximize the survival chances of society members, collective self-organization must balance individual interests with promoting the collective welfare. Although situations where group members have equal optimal values are clear, how varying optimal values impacts group dynamics remains unclear. To address this gap, we conducted a self-optimization study of a binary system incorporating communication-enabled active particles with distinct optimal values. We demonstrate that similar particles will spontaneously aggregate and separate from each other to maximize their individual benefits during the process of self-optimization. Our research shows that both types of particles can produce the optimal field values at low density. However, only one type of particle can achieve the optimal field values at medium density. At high densities, neither type of particle is effective in reaching the optimal field values. Interestingly, we observed that during the self-optimization process, the mixture demixed spontaneously under certain circumstances of mixed particles. Particles with higher optimal values developed into larger clusters, while particles with lower optimal values migrated outside of these clusters, resulting in the separation of the mixture. To achieve this separation, suitable noise intensity, particle density, and the significant difference in optimal values were necessary. Our results provide a more profound comprehension of the self-optimization of synthetic or biological agents' communication and provide valuable insight into separating binary species and mixtures.

Evaluation of the effect of a novel substrate that is composed of landfill-mined-soil-like-fractions on plant growth and heavy metal accumulation.

In the pursuit of a safe, low-cost, and sustainable method for the reuse of landfill-mined-soil-like-fractions (LFMSFs), pot experiments were conducted using seven growth substrates consisting of LFMSFs, tea residue, and peat for the cultivation of Photinia × fraseri. Six of the substrates had 40 %:60 %, 60 %:40 %, and 80 %:20 % volume ratios of LFMSFs to tea residue or peat, and one substrate consisted entirely of LFMSFs. The physicochemical properties of the substrate, growth parameters of the plants, and heavy metal content in the different pots were determined after one year of growth. The results indicated that the physicochemical properties of the substrate, that was composed of a mixture of LFMSFs and tea residue showed a significant improvement in organic matter, nitrogen, phosphorus, and potassium. However, there was also an increase in the salt and heavy metal contents when compared with those of peat. The plant growth in the LFMSF and tea residue substrate was slightly lower than that in the LFMSF and peat mixture. Notably, the best plant growth and environmentally friendly effects were observed when LFMSFs were added at 40 %. Additionally, most of the heavy metals were primarily removed from the substrate through the leaves of the seedlings, with the heavy metal contents being relatively low. In conclusion, LFMSFs as a cultivation substrate, represent a practical approach for reutilization, which could contribute to the reduction of reliance on traditional resources.